A large number of different carbohydrates exist, including many compounds of importance in biological processes. Carbohydrate structures can occur alone, but sometimes also occur in association with biomolecules such as lipids (glycolipids, glycosphingolipids), proteins (glycoproteins, proteoglycans), or other molecular structures. Carbohydrates are made up of a variety of different monosaccharide units or building blocks, which may occur along, e.g. as glucose or fructose, or which may be linked by a range of different glycosidic bonds to form larger molecules such as disaccharides, e.g. lactose and sucrose, oligosaccharides and polysaccharides, e.g. cellulose and starch. Larger units may be linear or they may have a branched structure, e.g. as shown in FIG. 1, where Mn represents monosaccharide type "n".
Given two monosaccharide units (say M1 and M2) linked in a particular way it is often possible to find reagents or groups of reagents (such as the enzymes known as glycosidases which cleave glycosidic bonds between monosaccharide units) which will selectively cleave the bond between M1 and M2 or between a monosaccharide and the molecular structure to which the monosaccharide is attached.
Given a suitable set of reagents e.g. enzymes, it is possible to cleave a carbohydrate structure in many possible ways, and to obtain a collection of different fragments which can be analysed by various separation methods such as by chromatography. From a knowledge of the resulting fragments it is possible to make various deductions concerning the structure of the original carbohydrate. This type of approach is described in, e.g., the paper by Tomiya et al. in Analytical Biochemistry, 163, 484-499 (1987).
However there are limitations to the known techniques, and the present invention aims to provide improved methods, and apparatus.